The present invention relates to a method for processing fish meat contaminated with sporozoa. More specifically, it is concerned with a method for processing fish meat of fish containing jellied meat due to contamination with sporozoa, whereby it is possible to produce "neriseihin" (fish meat paste products) having adequate elasticity from the meat having jellied meat which otherwise cannot be used as a raw material for "neriseihin" because of its lack of gel-forming capability.
When salt is added to raw fish meat undergoing grinding, myosins, which are soluble, in salt solution are dissolved out from the meat to form a "sol", which is very adhesive. When this adhesive raw ground meat is heated, the "sol" converts to "gel", which forms a network construction, and this gel imparts elasticity to the fish meat paste. Such elastic fish meat is called "neriseihin" (Japanese style fish meat paste product) in Japan, and fish meat which forms a strong "gel" is referred to as fish meat having a good gel-forming capability.
In Japan, unique types of coagulated fish meat pastes have been processed from ancient times. Although their origin is not entirely known, the Japanese style fish meat paste is said to have been processed as early as in the 15th century, according to old literature. The first product was "chikuwa" (literally "bamboo-ring") which is ground fish meat paste coated around a bamboo stick to a considerable thickness and heated. When the bamboo is pulled out after the processing, the coagulated fish meat paste forms a tubular round rod. The name "chikuwa" remains and the form has been kept to the present time. Next, the paste piled up on a thin rectangular wooden board appeared. This has been called "kamaboko". Thereafter, "hanpen" and "sumaki" appeared. "Hanpen" is a small disc-shaped fish meat paste product, and the raw material and processing method thereof and of "sumaki" are almost the same as those of "kamaboko" except for the appearance of the exterior which is covered with straw. The present Japanese style coagulated fish meat paste products thus derived from ground fish meat are of various shapes, and various heat coagulation methods are employed in their production.
The various kinds of Japanese style fish meat paste products are classified according to heating method as follows: Steamed articles: "mushi-kamaboko", "sumaki", etc.; broiled articles: "yaki-kamaboko", "yaki-chikuwa", "datemaki", "atsu-yaki", etc.; fried articles: "satsuma-age", "age-kamaboko", etc.
Jellied meat is also called "milky meat", "chalky meat", etc., and this generally refers to jellied fish meat which is spotted or soft as a whole. The jellied meat gives off no offensive smell and exhibits no significant variation in pH. This is a unique phenomenon of fish meat which is entirely different from decomposition or putrefaction. It is known that jellied meat occurs in fishes on which a certain kind of sporozoa is parasitic. Jellied meat does not occur while the host fish on which sporozoa are parasitic is living, but develops and rapidly propagates after the host has died due to the action of the sporozoa that are parasitic on the host. For this reason, it is very difficult to discern the initial change from outer appearance. Further, because there has hitherto been no appropriate countermeasure against the progress of such a phenomenon, jellied meat has been occurring in fish a very short time after they are caught, detracting greatly from their commercial value.
The sporozoa to which jellied meat is ascribable belong to the Unicapsla genus, Chloromyxum genus, Kudoa genus and the like of Myxosoporida which belongs to Cnidosporidae, Sporozoa of Protozoa. These sporozoa in themselves have a parasitic characteristic with respect to hematocryal vertebrata comprised primarily of fishes and are never parasitic with respect to human beings. Accordingly, the jellied meat when eaten is harmless to the human body. It is apparent that in the countries, e.g., Japan, where fish are customarily eaten raw, jellied meat in its initial stage is undoubtedly being unconsciously eaten. However, there has been no incidence of health trouble attributable to jellied meat. Much less would a "neriseihin", which is subjected to heat treatment, present any problem what so ever from the standpoint of food sanitation. Moreover, the term "sporozoa", as used herein, refers to Myxosporida.
Attempts have heretofore been made to utilize the fish meat of fish containing jellied meat as a raw material for "neriseihin". However, all of these attempts have as yet failed to produce satisfactory results. In general, in order to make a high quality "kamaboko" which has high elasticity, chopped fish meat must be soaked in cold water for several hours to remove fat, blood, odorous substances, and water-soluble proteins. The cold water is changed two or three times during the soaking. In general, the less fresh the fish meat is, the longer is the soaking time required.
Now, in the case of meat obtained from fish containing jellied meat, even when the frequency of the process of soaking in water is increased, or the soaking and dehydration procedures are carefully conducted, or the addition ratio of sugar or condensated polyphosphates is increased, the dehydrated fish meat has little gel-forming capability and is unsuitable for use as a raw material for fish-based "neriseihin", such as "kamaboko" and "chikuwa", which require a high gel-forming capability. Also, even when such dehydrated fish meat is incorporated into a normal raw ground fish meat, it reduces the gel-forming capability of the normal raw ground fish meat and, in extreme cases, results in a total loss thereof. Accordingly, fish meat containing jellied meat cannot be used even as a filler in normal raw ground fish meat. The fact is that a "neriseihin" raw material having a commercial value has not been obtainable from the meat of fishes containing jellied meat.
In view of the above described circumstances, we have carried out studies toward making the abundantly available but unused protein resources commercially useful and valuable, i.e., toward providing a method for processing the meat of fish containing jellied meat by which the fish meat can be used as a raw material for "neriseihin". As a result, we have found that by adding egg white to the meat of fishes containing jellied meat, it is possible to produce from the fish meat a "neriseihin" having a characteristic elasticity and to prevent any marked reduction in gel-forming capability that is encountered upon addition of the fish meat of fishes containing jellied meat to normal raw ground fish meat. This invention is based on these findings.